Cement compositions employing novel methacrylate monomer

ABSTRACT

1. IN A DIRECT DENTAL FILLING SYSTEM UTILIZING A BINDER ND FINELY DIVIDED SOLID FILLER HAVING AN AVERAGE PARTICLE SIZE OF SUBMICRON TO ABOUT 25 MICRONS WITH THE AVERAGE PARTICLE SIZE BEING WITHIN THE RANGE OF ABOUT 15-30 MICRONS, AN INTIMATE MIX OF MONOMER BINDER AND FINELY DIVIDED INORGANIC FILLER WITH THE FILLER BEING PRESENT IN AN AMOUNT IN EXCESS OF 50% BY WEIGHT OF SAID MIX AND AT LEAST 10% BY WEIGHT OF SAID MONOMER BINDER CONSISTING OF THE MONOMER 1,3-BIS(2,3-DI(METHACRYLOXY)-PROPOXY)= BENZENE.

United States Patent Office 3,845,009 Patented Oct. 29, 1974 3,845,009 CEMENT COMPOSITIONS EMPLOYING NOVEL METHACRYLATE MONOMER Robert Johns Gander, Whitehouse, NJ., assignor to Johnson & Johnson No Drawing. Continuation-impart of abandoned application Ser. No. 223,369, Feb. 3, 1972. This application Oct. 29, 1973, Ser. No. 410,732

Int. Cl. C08f 7/10, 45/04; C08g 33/10; C09k 3/00 US. Cl. 260-4215 12 Claims ABSTRACT OF THE DISCLOSURE Improved dental restorative cements are prepared from a new class of methacrylate monomer 1,3-bis[2,3-di- (methacryloXy)-propoxy] -benzene (-RGTMA). When the monomer is utilized as a binder for inorganic filler materials such as silane-treated crystal quartz filler, composite dental restoratives having substantially improved compressive strength and related physical strength properties are produced.

The present application is a continuation-in-part of eopending application Ser. No. 223,369 filed Feb. 3, 1972 and now abandoned.

BACKGROUND OF THE INVENTION Field of the Invention This invention relates to improved cement compositions useful as dental restoratives, the compositions containing a novel monomeric binder. More particularly, it relates to direct dental filling systems utilizing improved dental compositions of the composite type wherein a novel methacrylate monomer, 1,3-bis[2,3-di(methacryloxy)-propoxy]-benzene (RGTMA), is employed as the binder or as a portion of the binder for the inorganic filler.

While the utility of the novel methacrylate monomer of the present invention is described in connection with particular embodiments advantageously employed as binders for dental restorative compositions, it should be understood that the utility of the monomer is not necessarily limited thereto. It may also be employed wherever its unique properties may be advantageously utilized, as those skilled in the art will recognize in the light of this disclosure.

Description of the Prior Art When said monomer is employed in dental composites for the direct filling of teeth, improved results are surprisingly achieved, as contrasted with certain prior art alternatives.

Typical of the prior art is the subject matter of US. Pat. 3,066,112. It discloses dental filling materials comprising vinyl silane-treated fused silica and a binder consisting of the condensation product of two moles of methacrylic acid and the diglycidyl ether of bisphenol A or alternatively two moles of glycidyl methacrylate with one mole of bisphenol A, the binder being referred to as BlS-GMA. Because of high viscosity, the BIS-GMA must be diluted to the consistency of a medium syrup by use of suitable reactive monomers, e.g., methyl methacrylate, ethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate. In use as a dental restorative, the treated silica powder containing a suitable catalyst such as benzoyl peroxide is mixed with the syrupy liquid organic material which contains a suitable activator; and the mixed aggregate is promptly placed in the cavity to be filled wherein it hardens by polymerization of the organic material.

Such prior art dental restorative compositions have become known as composites and represent a very useful class of restorative materials in modern dental technology, a number of which are now commercially available. However, as documented by Mr. Frank H. Freeman of Kerr Manufacturing Company, Detroit, Mich. in a paper delivered in Houston, Texas on Mar. 21, 1969 before the Dental Materials Group, North American Division, International Association for Dental Research, restoratives of this type generally had compressive strengths in the range of about 28,000 to 34,000 pounds per square inch. For certain purposes such as posterior restorations, higher compressive strengths are desired, with the result that silver amalgam restoratives were generally preferred over the composite type restorative materials for posterior teeth because of the, higher compressive strengths attainable, such as on the order of 40,000 psi.

or more.

Objects of the Invention It is therefore an object of this invention to provide a new composition of matter which is particularly suited for use as an improved binder in dental restorative compositions of the composite type. It is a related object to provide dental restorative compositions of the composite type which exhibit desirably high compressive strength. It is a further object to provide dental restorative compositions which have all the advantages associated with prior art composite-type restorative compositions and fewer of the shortcomings.

It is another object to provide a binder for compositetype dental restoratives which does not require the addition of reactive diluents to control viscosity. It is still another object to provide a binder for composite-type dental restorative composiions which may be admixed with prior art binders to improve overall strength characteristics. These and other objects of the present invention will become apparent as the detailed description thereof proceeds.

SUMMARY OF INVENTION These objects are achieved by utilizing in the monomeric binder system the new monomer 1,3-bis[2,3-di- (methacryloxy)-propoxy]-benzene (RGTMA). To form the restorative composite the binder is mixed with a major proportion of the inorganic filler material such as silane-treated fused silica, the latter generally making up more than 50% by weight of the resulting composite, e.g., about to 90%, preferably about to by weight.

After polymerization and setting, the composite forms a hard, water-insoluble filling material having desirably high compressive strength. Further details are set forth in the following subsections and illustrative examples.

The Monomer Binder of the Invention As above indicated, the novel monomeric binder is 1,3- bis[2,3 di(methacryloxy) propoxy] benzene. This monomer may be represented by the following formula:

densed with methacrylic acid to produce a dimethacrylate which is then esterified with methacrylyl chloride:

diglycidyl ether of resoreinol methacrylic acid 0 C H2 0 C H:

dimethaerylate methacrylyl ehlorlde H Ha CHzCHCHzO 0 CG=CH:

1, 3-bis [2, 3-di (methaeryloxy)-propoxyl-benzene (Formula I) For convenience in discussion, this monomer is also referred to herein by the abbreviation RGTMA. Homopolymers of the 1,3 bis[2,3-di(methacryloxy) -propoxy]- benzene (RGTMA) monomer are found to have an index of refraction of 1.590. This is a relatively high index of refraction as compared to most monomers that might be used in binder systems for filled composite restoratives and makes this novel monomer particularly useful for blending with other monomers having homopolymers of lower refractive index where it is desirable to substantially match the refractive index where it is desirable to sub stantially match the refractive index of the binder polymer with that of the filler where fillers such as quartz, having relatively high refractive indexes are used. The refractive index of quartz being 1.545.

Dental Restorative Compositions of the Invention The new methacrylate ester monomer 1,3-bis[2,3-di- (methacryloxy)-propoxy]-benzene (RGTMA) described above affords particular advantages when used as a binder for inorganic filler materials. In particular, with use of the new monomer, hard, water-insoluble dental restorative compositions having desirably high compressive strengths can be readily prepared. Moreover, the low viscosity of the monomer composition permits its use in the formulation of composite restorative compositions without the need of viscosity reducing diluents. Also, it will be understood that other polymerizable monomers, including the aforementioned BIS-GMA, can be included in the dental compositions along with the new monomer of this invention, if desired, and improvements in compressive strength be obtained.

The 1,3 bis[2,3 di(methacryloxy) -propoxy]-benzene (RGTMA) should, however, be present in the binder system in amounts of a least by weight of the binder monomers.

As already indicated, composite restorative compositions in accordance with this invention are prepared by mixing the said monomer composition with a major proportion of a particulate inorganic filler material, the latter generally making up more than 50% by weight of the resulting composite. Thus, for example, where a paste-like consistency is desired as where the composite restorative composition is to be used for the filling of prepared cavities and. the like the inorganic filler material would be present in amounts of about 70 to 90% by weight, preferably in amounts of about 75 to 85% by weight. Where a more fluid consistency is desired, however, such as in the treatment of pits and fissures in teeth where the surface of the tooth is coated, the amount of filler used would be substantially less with filler contents of slightly over 50 weight percent being useful. A variety of inorganic filler materials can be employed-Representative of such materials are silica, glass beads, aluminum oxide, crystalline quartz and the like. The particle size of the filler material generally ranges from submicron to about microns with the average particle size being in the range of about 15 to 30 microns and preferably is in the range of about 20 to 25 microns.

The particulate inorganic filler material should preferably be treated with a keying agent to improve the binding of the resin thereto. Keying agents and the method of use can be as described in the aforementioned US. Pat. 3,066,112. Keying agents which have been found to be particularly suitable are the high performance ethylenically unsaturated organosilane compounds such as gammamethacryloxypropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriacetoxysilane and the like.

Initiation of polymerization which causes the composite to set into a hard mass is conveniently effected at room temperature, e.g. about 25 to 30 C., by inclusion in the formulation of a peroxide polymerization catalyst and an activator which functions to cause a rapid decomposition of peroxide with the resultant formation of polymerization-inducing free radicals.

A variety of peroxide polymerization catalysts as known in the art can be used, benzoyl peroxide, 2-4-dichlorobenzoyl peroxide and 4*chlorobenzoyl peroxide being representative thereof. The catalyst is generally employed in amounts from 0.01 to 1.0% by weight based on the weight of the restorative composition.

Similarly, an activator or accelerator material which causes decomposition of the catalyst is employed in the formulation, such as, for example, N,N-dialkylanilines and N,N-dialkyltoluidines. The activator is generally employed in amounts ranging from about 0.01 to 1.0 weight percent based on the Weight of the restorative composition. While various activators can be used, amine activators of the type represented by the following formula are particularly effective.

wherein R is hydrogen or methyl and X is methyl, ethyl or hydroxyethyl. A preferred activator is N,N-di(2- hydroxyethyl) -p-toluidine.

For convenience in use, the composite dental filling compositions can be formulated in the form of pastes adapted for ready mixing by the dentist or other user. Thus, a paste (-A) can be formulated containing the resinforming monomer, inorganic filler and activator while a second paste (B) can contain the monomer, filler and peroxide, approximately the. same proportions of monomer and filler being present in each paste for convenience, although not necessarily limited to such proportions. Upon mixing of the two pastes, polymerization of the monomer or monomers is initiated With the Working or hardening time being variable and controllable by use of more or less of the activator.

A typical formulation for pastes A and B in this embodiment would be as follows:

EXAMPLES The following examples, which are presented to amplify the description set forth hereinabove and are not to be considered limiting, illustrate the preparation of 1,3-bis- [2,3-di(methacryloxy)-propoxy]-benzene and the formulation and properties of representative dental restorative compositions produced therefrom.

Example l.New Monomer Composition In a 2-liter, 3-neck flask are placed '600 g. (5.10 epoxy equivalents) of resorcinol diglycidyl ether; 430 g. (5.00 moles) methacrylic acid; 5.0 g. triphenylphosphine and 0.5 g. p-methoxyphenol. A water condenser is mounted on the flask and the contents are stirred continuously for 48 hours while heating in an oil bath at 80-85 C. The reaction mixture at this point is essentially 1,3-bis(3meth acryloxy-2-hydroxypropoxy)-benzene, a yellow, viscous liquid with the following properties:

Weight per epoxy equivalent: 33,643 Acid Number: 3.2 mg. KOH/ gram n 1.5268

A solution of the following is dried overnight over grams of Type 4A molecular sieves: 1,3-bis(3-methacryloxy-2-hydroxypropoxy)-benzene, 100 g. (0.51 mole); acetone, Reagent Grade, 150 ml.; triethylarnine, 51.6 g. (0.51 mole); p-methoxyphenol, 0.04 g. The dried solution is filtered into a 500-ml., 3-neck flask bearing a thermometer, condenser, mechanical stirrer and dropping funnel. The solution is stirred and cooled intermittently in an iceand-water bath to maintain the temperature in the 24 to 30 C. range while 53.2 g. (0.51 mole) of redistilled methacrylyl chloride (b.p. 43/ 96 mm.) is added during one hour.

The reaction mixture is poured into 600 g. of water and 200 g. of ice. The water is extracted with two 400-ml. portions of diethyl ether. The combined ether extracts are washed successively with two 100-ml. portions of 5% sodium bicarbonate solution and two 100-ml. portions of water. The washed ether solution is dried over molecular sieves, filtered, and 0.012 g. of phenothiazine added. The ether is evaporated at water pump pressures and the last of it removed at 4 mm. pressure. The product, 1,3-bis[2,3-

di(methacryloxy)-propoxy] -benzene (RGTMA), is a mobile yellow liquid with a pleasant odor which weighs 73.3 g.; n 1.5058. When the monomer is polymerized, homopolymer formed of the same has a refractive index of 1.590.

Example 2.Dental Restorative Utilizing Novel Monomer (RGTMA) In Composite With 80%. Quartz Filler Crystal quartz is ground in a porcelain ball mill to a size which will pass through a 200-mesh screen. The size range of the particles is from 75 microns to less than one micron with a median size of about microns. The ground quartz (500 grams) is placed in 1000 milliliters of 20% hydrochloric acid and heated to 80 C. for an hour. The acid is filtered, and the quartz is washed with water until effluent water reaches pH 6 to 7. The quartz is then dried in an open glass tray at 130 F.

A water solution of silane is prepared by placing 0.4 milliliter of acetic acid and 10 grams of gamma-methacryloxypropyltrimethoxysilane in 200 milliliters of water and stirring rapidly at room temperature. A slurry is made of the acid-washed quartz and the silane solution.

The liquid is then sucked from the quartz on a ceramic filter, so as little water as possible remains on the quartz. The quartz is again dried at 130 F. on a glass tray. It is stirred frequently during drying to prevent caking. The resulting silane-treated quartz is employed in preparing two pastes hereinafter described.

Two pastes are prepared which are substantially identical in composition except that one contains benzoyl peroxide as an additional component and the other contains N,N-di(Z-hydroxyethyl)-p-toluidine. Monomer, 1,3-bis[2, 3-di(methacryloxy)-propoxy]-benzene (RGTMA), prepared as set forth in Example 1, is the only monomer in this system. The compositions of the pastes are as follows:

Parts by Percent by weight weight Equal parts by weight of Pastes A and B are mixed for 30 seconds and then packed into cylindrical Teflon molds, 0.158 inch in diameter and about 0.31 inch in length, the ends of the molds being covered with smooth glass plates. After three minutes hardening occurs, and the molds are immersed in water at F. for 24 hours. The composite cylinders, which contain 78% quartz filler, are then expelled from the Teflon molds, accurately measured, and tested. Ten cylinders are crushed in compressive strength tests using an Instron tester, and another ten cylinders are crushed in determination of the diametrical tensile strength. Compressive strength is found to be 41,40621384 p.s.i. and tensile strength is found to be 7,1741243 p.s.i.

This two-paste system is used to place a mesio-occlusal Class II restoration in the maxillary right second premolar of a dental patent. The tooth is prepared for filling by conventional drilling techniques such as those used prior to placing silver amalgam restorations. The base or the cavity is lined with a zinc oxide-eugenol cement base. A metal matrix band is then placed around the tooth, and wedges are placed to avoid overhangs and to provide proper axial contour.

Approximately equal amounts of Pastes A and B are mixed on a coated paper mixing pad for about 20 seconds. The mixed paste is then inserted using normal packing pressure to fill under-cuts. The restorative gels to a hard composition about two minutes after insertion. Five minutes after insertion the matrix band is carefully removed. The filling is finished with a fiine, water-cooled diamond stone, then with a fine green stone, and finally with a lubricated fine white stone. The finished restoration is strong and durable.

Using the same binder and filler as in the preparation of the foregoing Pastes A and B, a more fluid mix is prepared by increasing the proportion of binder. The slurries as prepared have the following composition:

Parts by Percent by Prior to coating teeth with the above sealant compositiori the patients mouth is first rinsed with an oral antiseptic and then with water. The teeth are isolated with cotton rolls, thoroughly dried with an air syringe, and etched for approximately one minute with phosphoric acid. The mouth is again thoroughly rinsed with water to remove the acid from the tooth surface. The teeth are then again isolated with cotton rolls and thoroughly dried. Approximately equal proportions of Slurry A and Slurry B are mixed with a glass stirrer and the mixture then coated on the teeth. After curing a firmly bonded resistant coating is obtained filling and sealing the pits and fissures of the treated teeth.

Although in the foregoing Example the polymerization of the binder monomers is initiated by mixing approximately equal parts of Slurry A and Slurry B, Slurry A could be used alone as the pit and fissure sealant with polymerization being initiated just prior to application through the addition of a small amount of benzoyl peroxide.

In the same manner Slurry B could be used alone with the addition of small amounts of amine activator just prior to application of the pit and fissure sealant to the teeth. 1

Example 3.Restorative Cement Compositions of 80% Crystalline Quartz Filler Having Matched Index of Refraction Following the procedure of Example 2, restorative cement compositions are prepared in which the binder system is formed of a mixture of the novel monomer RGTMA with other monomers to obtain a binder polymer having a refractive index substantially matching that of the crystalline quartz filler. The cement compositions are set forth in the following Table.

total weight of said mix, of amine activator for peroxide polymerization catalysts.

3. A direct filling system of claim 2 in which said amine activator is represented by the formulae TABLE FOR EXAMPLE 3 Restorative composites formed of by weight binder and 80% by weight quartz filler Percent Refractive index ofby wt based on Binder Cured Monomer composition of binder binder resin polymer Quartz composite 1,3-butanediol dimethaerylate (BGDMA) 33. 4 Composite 1 I di f i g x g g vf iggfiggzf GTMA) g 1. 545 1. 545 1. 545:];0. 005

riet ylene g ycc ime acry a e Composite 2 'i1,3-bis[2,3-di(methacryloxy)-propoxy]-benzene (RGTMA)- 55. 5 i 545 545 545:50 005 The advantages of dental restorative compositions in accordance with the invention are apparent from the foregoing. It will be seen that use of the new monomer composition of the invention as a binder with inorganic filler materials results in compositions having significantly improved compressive strengths and appearance. Such dental restorative compositions are particularly desired for use in filling teeth such as in posterior restorations where high compressive strength is desired and are particularly useful in preparing restorative compositions using quartz as the filler to obtain restorative composi tions of excellent appearance having substantially matched indexes of refraction.

From the above description, it is apparent that the objects of the present invention having been achieved. While only certain embodiments have been illustrated, many alternative modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered within the spirit and scope of the present invention, and coverage thereof is intended by the claims of any patents based on this application.

Having described the invention, what is claimed is:

1. In a direct dental filling system utilizing a binder and finely divided solid filler having an average particle size of submicron to about microns with the average particle size being within the range of about 1530 microns, an intimate mix of monomer binder and finely divided inorganic filler with the filler being present in an amount in excess of 50% by weight of said mix and at least 10% by weight of said monomer binder consisting of the monomer 1,3-bis[2,3-di(methacryloxy)-propoxy]- benzene.

2. A direct filling system of claim 1 in which said intimate mix contains 0.01 to 1.0% by weight, based on the 7. A direct filling system of claim 1 in which said monomer binder consists of the monomer 1,3-bis[2,3-di (methacryloxy)-propoxy]-benzene together with at least one monomer of the group consisting of 1,3-Butanediol dimethacrylate and Triethylene glycol dimethacrylate and said finely divided inorganic filler is crystalline quartz.

8. A direct filling system in accordance with claim 1 wherein the inorganic filler is present in an amount of about to 90% by weight.

9. A direct filling system in accordance with claim 1 wherein the inorganic filler is present in an amount of about to by weight.

10. A direct filling system in accordance with claim 1 wherein the inorganic filler is crystalline quartz having a particle size of submicron to about microns.

11. A direct filling system in accordance with claim 1 wherein the inorganic filler is treated with a silane material which improves binding of the binder thereto.

12. A direct filling system in accordance with claim 11 wherein said silane material is gamma-methacryloxypropyltrimethoxysilane.

References Cited UNITED STATES PATENTS 3,539,533 11/1970 Lee II et al. 260-47 3,635,889 1/1972 Bowen 26047 UA 3,730,947 5/ 1973 Stotfey 26047 UA ALLAN LIEBERMAN, Primary Examiner T. DE BENEDICTIS, SR., Assistant Examiner U.S. c1. X.R.

106-35; 260-47 UA, UP, 486 R, 42.52

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,8 5, 009 DATED October 29, 197" INVENTQRB) I Gander, Robert Johns It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: a

In Column 3, Line beginning with 31-32, delete first "where it is desirable to substantially match the refractive index" as it is repeated twice.

In Example 1, Column 6, Second under Paste A, the letters "N,N, should read "N,N".

In Column 6, Line 30, the word "the base or the cavity" should read "the base of the cavity".

In Column 6, Percent by weight, last "Silane" the figure "60.0" should read "50.0".

In Column 7, Line m, the word "having been achieved." should read "have been achieved".

Signal and Sealed this sixteenth Day of December 1975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer V Commissioner of Pa rents and Trademarlts 

1. IN A DIRECT DENTAL FILLING SYSTEM UTILIZING A BINDER ND FINELY DIVIDED SOLID FILLER HAVING AN AVERAGE PARTICLE SIZE OF SUBMICRON TO ABOUT 25 MICRONS WITH THE AVERAGE PARTICLE SIZE BEING WITHIN THE RANGE OF ABOUT 15-30 MICRONS, AN INTIMATE MIX OF MONOMER BINDER AND FINELY DIVIDED INORGANIC FILLER WITH THE FILLER BEING PRESENT IN AN AMOUNT IN EXCESS OF 50% BY WEIGHT OF SAID MIX AND AT LEAST 10% BY WEIGHT OF SAID MONOMER BINDER CONSISTING OF THE MONOMER 1,3-BIS(2,3-DI(METHACRYLOXY)-PROPOXY)= BENZENE. 